A charge storage capability of a capacitor is largely dependent on a size of a dielectric constant, a distance between two conductive plates, and areas of the conductive plates. Under conditions of the unavailability of a material with a higher dielectric constant and an irreducible distance between the conductive plates, an only feasible approach for increasing the charge storage capability is expanding the areas of the conductive plates. However, under current manufacturing processes targeting at integration and miniaturization, increasing the size of elements due to the increased area of the conductive plates contradicts current requirements on circuit elements. For example, the US Publication No. 20080048235 “Capacitor Structure and Method for Preparing the Same” discloses a capacitor structure. In the above prior art, a crown-shaped capacitor structure is described for increasing relative areas between electrodes through characteristics in a shape of the crown-shaped capacitor.
To further increase relative areas between electrodes, “Method of Manufacturing Charge Storage Device” is disclosed by the US Publication No. 20070161185, and “Method of Forming a Metal-Insulator-Metal Capacitor” is disclosed by the US Publication No. 20080145997. In the above prior art, multiple insulator layers are stacked on a substrate, and an opening connecting to the substrate is disposed at the insulator layers. An etch solution etching the insulator layers in different materials at different etch rates is then utilized to laterally etch the insulator layers to form sidewalls of the opening to a plurality of recesses, thereby forming the crown-shaped capacitor structure. A capacitor process is then performed on surfaces of the sidewalls to achieve the object of increasing a sensing area of the capacitor.
The crown-shaped capacitor structure disclosed by the above prior art can be simplified to a structure shown in FIG. 1. Referring to FIG. 1, the crown-shaped capacitor structure includes a substrate 1, a lower electrode 2, and a dielectric layer 3 covering a surface of the lower electrode 2. It should be noted that a top electrode covering a surface of the dielectric layer 3 is not depicted to facilitate a clear description. The lower electrode 2 includes a bottom electrode 201 parallel to the substrate 1, and two side electrodes 202 perpendicular to the bottom electrode 201. The two side electrodes 202 are electrically connected to the bottom electrode 201 to form a so-called crown-shaped capacitor structure. The dielectric layer 3 covers surfaces of the bottom electrode 201 and the two side electrodes 202. Based on a large degree of freedom at an upper end of the side electrodes 202, a sphere 4 is formed when the dielectric layer 3 covers the upper end—such phenomenon is a natural occurrence in the manufacturing process. Due to large diameter of the sphere 4, an aperture ratio between the two side electrodes 202 is decreased. Further, the two spheres may be too close to connect with each other to seal the opening that results in difficulty in proceeding subsequent processes or even causing subsequent processes to be impracticable. Moreover, to maintain the charge storage capacity, a height of the side electrodes 202 needs to be increased to lead to a raised aspect ratio. Consequently, enhancing an overall manufacturing yield rate is made extremely challenging under such circumstances. Therefore, there is a need for a solution for overcoming the above issues.